Gasoline regulations limit the amount of sulfur that can be present in motor fuel.
One area of interest from automakers is the distillation index or drivability index (DI), which is a measure of gasoline tendency to vaporize. It is calculated from a gasoline's distillation profile. The specific formula for Drivability Index (DI) is DI(° F.)=1.5(T10)+3(T50)+T90. The variables T10, T50, and T90 are the temperatures (in degrees Fahrenheit) at which 10%, 50% and 90% of the fuel vaporizes, respectively, during a standard ASTM D86 distillation test. To have desirable emissions characteristics, it is preferred that the drivability index is below 1200° F.
Another area of interest from automakers is the Reid Vapor Pressure, which defined as the absolute vapor pressure of volatile crude oil and volatile non-viscous petroleum liquids. A lower Reid Vapor Pressure is desirable.
However, it is challenging to produce gasoline with both the desirable Reid Vapor Pressure and the desirable Drivability Index since Reid Vapor Pressure and Drivability Index tend to act in an opposite fashion in such that Reid Vapor Pressure decreases with an increase in T10 while DI increases with an increase in T10. For example, removal of the lighter fuel components such as nC4 and C5's will shift the T10 and T50 to higher values, resulting in an increase in the Drivability Index unless steps are taken to remove the heavier portion of the gasoline which may result in a significant lost in octane.
Therefore, a hydrocarbon upgrading process that can address the Reid Vapor Pressure and Drivability Index issues simultaneously would be a benefit to both the art and to the economy
U.S. Pat. No. 6,566,569 describes a process of dehydrogenation of pentanes, conversion to C4-C6 olefins then rehydrogenation to make alkanes/isoalkanes. However the dehydrogenation process is expensive and energy intensive and there exists a need to upgrade hydrocarbons without dehydrogenation.